When considering the retransmission of the television radio wave from the broadcasting satellite to the cable system there has been known the method whereby both of the video and audio signals are once demodulated to the baseband signals and another carrier wave is remodulated by the baseband signals to form the television signal of the standard system and this television signal is retransmitted within the band width of 6 MHz, because the radio wave from the broadcasting satellite has the wide band width of 27 MHz.
According to this method, the video signal can be efficiently transmitted. However, the merit of the pulse code modulation (PCM) system to improve the receiving quality in the audio transmission of the satellite broadcast is lost. The independent data other than the audio signal cannot be transmitted as well.
There can be also considered another method whereby the pulse code modulated (PCM) audio signal is transmitted within the band width of 6 Mz of one channel of the television. For example, there is frequency division multiplex (FDM) transmission method. In this case, however, there are the drawbacks such that the transmission capacity of FDM system per channel has less capacity than that of TDM system and when a plurality of audio signals are simultaneously amplified by the wide band amplifier, the intermodulation distortion is likely to occur.
As a method of avoiding such problems, it can be considered to time division multiplex a plurality of audio signals. In this case, however, with respect to the PCM audio signals when the radio wave was received from the satellite, the clock signal frequencies in the pulse code modulation of the respective audio signals generally differ slightly due to the difference of the originating stations (transmitting stations of programs). Therefore, it is difficult to obtain the time division multiplexed (TDM) signal using the common clock signal.